a) Field Invention of the Invention
The invention is directed to a gas sample vessel for a gas analyzer comprising a housing enclosing a cylindrical resonator cavity, two mirrors which limit the resonator cavity being fastened to the housing for coupling in and feeding back the measurement light proceeding from an illumination source.
b) Description of the Related Art
Measuring devices known as gas analyzers are used to determine the properties of a gas. Gas analyzers frequently have a cavity resonator, as it is called, which receives a gas sample and into which a light beam is coupled in a defined manner. The propagation of the light within the cavity is influenced depending on the properties of the gas. This influence is evaluated (intracavity gas analysis).
Resonators with cylindrical cavities limited at both ends of their longitudinal extension by mirrors with spherically curved mirror surfaces are known. A recurring problem in the production of resonators of this type consists in adjusting the mirrors in such a way that the reflected radiation is directed exactly in the center axis of the cylindrical cavity.
Gas analyzers of the type mentioned above are described in U.S. Pat. Nos. 5,432,610 and 5,450,193. These gas analyzers have sample chambers formed from a pipe piece which is provided with a mirrored inner wall and which is defined at both ends by mirrors whose position is adjustable. Through one of these mirrors, the in-coupling mirror, the measurement light beam coming from a laser light source reaches the interior of the gas sample chamber.
The coupled-in laser beam extends in the center axis of the gas sample vessel and it is necessary to adjust the mirrors in such a way that their focal point lies in the center axis.
Additional auxiliary devices are needed during adjustment to move and hold the individual elements because both the in-coupling mirror and the opposite end mirror must be moved relative to the pipe piece in several degrees of freedom for exact orientation and, finally, must be held in the correct position until fixed.